Photonic Frequency Down-Converter Based on a Frequency-Doubling OEO Using Two Cascaded EAMs

A photonic frequency down-converter based on a frequency-doubling optoelectronic oscillator (OEO) using two cascaded electro-absorption modulators (EAMs) is proposed and experimentally demonstrated. The use of the two cascaded EAMs allows the OEO feedback loop used to generate the local oscillator (LO) signal and the down-conversion section to be structurally isolated, so that the proposed photonic frequency down-converter has high RF to LO isolation. The phase noise of the frequency-doubled 20-GHz LO signal and that of the downconverted 3-GHz IF signal were measured to be -97.80 and -95.32 dBc/Hz at an offset frequency of 10 kHz, respectively. The spurious free dynamic range measured using a two-tone test was 87.02 dB · Hz
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. The bit error rate performance was also investigated with a 20-GHz RF signal modulated by 1.25 Gb/s data.